Weed Wednesdays

What are Annual Plants?

Annual plants complete their life cycle in one year meaning they go from germination, to flowering stalk to seed all in on year. There are two types of annuals: winter and summer annuals. 

Winter annuals live their life cycle throughout the winter; germinating in the fall, wintering over as a rosette then produce seed in the spring. They die back in late spring/ early summer completing their life cycle before summer. Good examples of this are Downy brome and Jointed goatgrass. Summer annuals, like Himalayan balsam, germinate in the spring and complete its life cycle by the end of the summer. The recommended time to control winter annuals is in the fall from mid-October to freeze up. Winter annuals can be controlled in the spring as well, but it is best to do early before these plants begin actively growing and green- up. 

For any further information on plant life cycles, you can contact the Agricultural and Environmental Department or stay tuned for more Weed Wednesday posts! 

What are Biennial Plants?

Biennial plants live for two growing seasons. Their first year they produce a basal rosette and then in the second year they grow into a flowering stalk producing seeds. These biennials die back in the fall and do not return the following year. A basal rosette is a circle of leaves that lay close to the ground and radiate from the center point, typically the taproot. The fall is a great time to control these biennial plants while they are in the rosette stage.  

Examples of biennial weeds are common mullein, black henbane and blueweed. For any further information on plant life cycles, you can contact the Agricultural and Environmental Department or stay tuned for more Weed Wednesday posts! 

What are Perennial Plants?

Perennials are plants that live more than three years and continue to come back year after. Some perennials can have substantial life spans; trees are a good example. Perennials typically have vegetative reproduction structures that enable them to reproduce without seeds. These can include stolons, rhizomes, bulbs, or tubers. There are two types of perennial plants: simple and creeping perennials.

Simple perennials grow as individual plants and have tap roots. They may regenerate after being cut or injured but typically reproduce by seed. The creeping rooted perennials have many horizontal creeping stems, such as rhizomes and stolons, that radiate out from the parent plant allowing it to generate tubers and/or new plant shoots.

An example of a simple perennial weed is baby’s breath, and examples of creeping perennial weeds are Canada thistle and Creeping bellflower. Perennials are best controlled when they are still growing in early fall, generally before harvest time. For further information on plant life cycles, contact the Agricultural and Environmental Department.

What is the Weed Control Act?

The Weed Control Act was established in 1907 making it one of Alberta’s oldest pieces of legislation. The Weed Control Act was developed to manage invasive weed species and protect Alberta’s native vegetation and agricultural crops. Invasive species present significant risk not only ecologically, but socially and economically. The Weed Control Act defines weeds in two categories: Noxious and Prohibited Noxious. 

Noxious weeds are generally found throughout the province and have negative effects on the ecosystems and Alberta’s agriculture. It is the responsibility of the property owner or occupier to control and prevent further spread of these noxious weeds. To control, means to inhibit the growth or spread, and/or destroy. 

Prohibited noxious weeds are generally only found in small numbers in Alberta or not found at all. Early detection and rapid response help prevent these weeds from becoming established in the province. It is the responsibility of the landowner or occupier to destroy these weeds. To destroy, means to kill all growing parts of the weed and to render the reproductive mechanisms of the weed non-viable.

There are 75 regulated weeds in the province of Alberta, 46 of which are prohibited noxious and 29 are noxious. For a full list of these regulated weeds, you can find them in the Weed Control Regulation, or by visiting the following link:

Provincially regulated weeds | Alberta.ca

To learn more about the Weed Control Act or Weed Control Regulation, please contact the Agricultural and Environmental Department or visit the following link:

Manual (gov.ab.ca)

Black Henbane

NOXIOUS Black Henbane (Hyoscyamus niger) is a biennial weed flowering from July to September. This plant is poisonous to humans and livestock and should be removed carefully. Black henbane originated in the Mediterranean and belongs to the Nightshade family. The bell-shaped flowers are cream coloured with dark purple veins and 5 lobes. There are usually a few flowers per stem which have a garbage-like odour. Black henbane produces a basal rosette in the first year that has prominent white mid-vein, and the leaves are covered with hairs. The second year, this weed grows up to 1 m tall and the entire plant is covered with hairs. The extremely large, bell-shaped seed capsules are papery thin with triangular edges. The seed capsules are typically aligned on one side of the stem and leave a woody skeleton after seed set. One Black henbane plant can spread up to 500,000 seeds! This is a unique looking plant which makes it easier to identify! The best way to control these weeds is by hand-pulling, mowing, herbicides, and cutting at the base of the plant and/or rosette. 


Blueweed (Echium vulgare) is a biennial in the Boraginaceae family. If you live in the Crowsnest Pass you have probably seen this noxious plant before! Blueweed is unpalatable to grazers and is potentially poisonous due to toxic alkaloids.  

This invasive weed has numerous funnel shaped flowers, often purplish-blue in colour but can also be pink or white. The entire plant is covered in bristly hairs that can cause skin irritation, so be sure to wear gloves when handling this noxious weed. In its first year it produces a basal rosette that radiates from the center point. Flowering stalks grow from the rosette producing flowers in the upper side of short, arching branches. The black taproot has some fibrous lateral roots and can be difficult to remove. Blueweed prefers growing in dry, rocky areas, gravelly riparian areas, roadside, pastures, and meadows at mid to low elevations. It requires well drained soils and does not tolerate shade very well. If you are removing Blueweed rosettes from your yard, the best way is to try and remove majority of the root or sever below the soil line when the soil is moist. If any portion of the plant has flowered or has seed heads formed, carefully remove and bag. Blueweed reproduces by seed which can spread by water, heavy machinery and vehicles, animals, infested gravel, or by use of commercial seed and hay. Do not place lawn trimmings in compost if they may contain blueweed seeds. For any additional information on how to treat Blueweed, please contact the Agriculture and Environmental department.

Canada Thistle

Canada Thistle (Cirsium arvense) is a perennial plant that made its way to Canada through contaminated crop seed from Eurasia. It develops a rosette in its first year then reproduces through deep, spreading roots and by dispersing seeds that can remain viable for 21 years.  

This plant belongs to the Sunflower family and produces a purple- pink flower and has bracts with no spines. The leaves are glossy, alternately arranged, spine-tipped and stalkless with wavy edges. The stems are erect with prickly spines and can be slightly hairy. The Canada Thistle can grow up to 120 cm tall and is supported by creeping roots that can spread 4.5 m wide and 6 meters deep! This is the only thistle that has both male and female flowers.

You can find Canada Thistle just about anywhere in the province of Alberta. They are drought resistant and thrive in a variety of soil types in disturbed areas, crop and pasturelands, grasslands, stream banks and urban areas. This weed is problematic because it outcompetes vegetation causing severe crop-yield losses, reduces access and nesting cover for waterfowl.  Repeated cultivation, mowing, or hand-cutting reduces infestations and can eventually eliminate the plant.

Common Burdock

Common Burdock (Arctium minus) was the inspiration for Velcro by George de Mestral in the 1940’s. It’s prickly seed heads spread by sticking to anyone or any animal that brushes up against it. These burrs may be great for inspiring Velcro but are an issue for small birds and bats when they become entangled. These burrs are not only difficult to deal with for small animals but also for horses and sheep when the burrs become trapped in their manes and de-value the sheep’s wool.  Common burdock has large leaves that can prevent sunlight and water to reach other plants, so you don’t typically get other plants growing near a burdock infestation. It is a biennial plant in the sunflower family, native to Eurasia and if often found in areas where the soil has not been disturbed. It prefers farmland, pastures, barnyards, fence rows, stream banks and forest open areas, edges, and understories.  

Often confused with Great Burdock and Wooly burdock, it can be differentiated by the size of the flowers and burrs, although, all three of these burdock species are regulated as noxious weeds in Alberta. Seed production begins in July and continues in the autumn spreading up to 16,000 seeds per plant.

You can treat this plant with herbicides, hand-pulling, digging, or cultivating prior to seed set. It tolerates a range of soil conditions and prefers full to partial sun.

Common Mullein

Common Mullein (Verbascum thapsus) also known as Cowboy’s toilet paper due to its large, and very soft, felt-like leaves. This plant can be easily identified in its basal rosette stage or its erect flowering stem in the second stage of growth. The stems are woody and can grow up to 2.5 m tall, have a candle-stick appearance with 5-petaled, yellow flowers. This is a biennial plant in the Figwort/ Snapdragon family, native to Europe. This plant was used as a fish poison and brought over as a medicinal plant to treat an array of ailments but unfortunately has proven to displace native vegetation and overtake disturbed areas. Also, this plant is thought to serve as an alternate host for insects that negatively affect pears and apples.  

Common Mullein can produce up to 250,000 seeds per plant. The seeds generally don’t spread far from the plant but are viable for over 100 years making eradication difficult once established in an area. You can hand pull the entire plant but if there are flowers or seeds present you will want to bag and burn the flowered stems. The rosettes are easy to hand pull and can be controlled with herbicides.  

For large Common Mullein infestations, please contact the Agriculture and Environmental department to learn more about how to control this invasive weed! 

Common Tansy

Common Tansy (Tanacetum vulgare) is a perennial plant that was brought over as an ornamental from Europe. It is mildly toxic to humans and wildlife if consumed. You can identify these plants by their button-like yellow flowerheads that form dense clusters of 20-100 on the stem ends. Leaves have alternate arrangement; they are consistent in size and have deeply toothed margins giving it a fern-like appearance. These leaves will have a strong odour when crushed. Stems are often purplish-red, erect and woody. They can also be identified by their old woody skeletons from previous years. These plants prefer areas with full-sun and well-drained soil. You often see them roadside and along riparian areas. These plants can be upwards of 1.8 m tall and reproduce by seed and creeping roots. Common Tansy can produce up to 50,000 seeds which remain viable for up to 25 years. These plants can be controlled by cutting, mowing and herbicide application.

Creeping Bellflower

Creeping Bellflower (Campanula rapunculoides) is a creeping perennial that was introduced as an ornamental from Europe. You can identify these plants by their purple-blue, bell-shape flowers that have 5 fused petals, 5 green sepals and nodding flowers. The leaves are alternatively arranged and have a wide range in leaf variability but will generally be heart shaped with jagged edges. Often confused with the native Bluebells, the Creeping Bellflower is usually much taller, upwards of 100 cm, has larger flowers and creeping roots.  The Creeping Bellflower is a common lawn weed and is difficult to eradicate because it can reproduce by seed and aggressive thick creeping rhizomes. These plants can produce up to 15,000 seeds per plant! The best control methods include hand-pulling, digging, and smothering with tarps or cardboard.  

Dalmatian Toadflax

NOXIOUS Dalmatian Toadflax (Linaria dalmatica) is native to southeast Europe. The species name dalmatica, refers to the Dalmatia region of Croatia. Dalmatian toadflax is a short-lived perennial plant belonging to the Snapdragon family, flowering from June to September. 

It is mildly toxic to livestock and can reproduce by seeds or creeping roots. It has yellow snapdragon-like flowers with a darker yellow spot on the lower lip, sometimes appearing orange. The leaves are waxy, similar to how tulip leaves feel, and are pale blueish-green. The leaves are oval to heart shape with pointed tips and clasp the stem. This weed can grow to 120 cm tall and can have multiple branches growing off the stem. This toadflax has a deep, woody taproot with horizontal roots that can form new plants and spread up to 500,000 seeds. Dalmatian toadflax’s flowers are almost identical to those found on Yellow Toadflax although the leaves on the two weeds are very different. Yellow toadflax leaves are lanced shaped and attached directly to the stem without clasping. 

Dalmatian Toadflax can grow in disturbed areas, grasslands, pastures, and residential areas. Repeated hand-pulling and herbicide are appropriate control measures for this weed. Dalmatian toadflax stem-boring weevil has been used as a bio control agent. 

Dames Rocket

NOXIOUS Dames Rocket (Hesperis matronalis) can be seen in the Crowsnest Pass from late June to August with its vibrant magenta flowers. These weeds outcompete native vegetation quickly with their early spring growth and dense cluster formations. The tooth-edged leaves are lance-shaped and have small hairs on both sides. The stems reach 1 m tall and stabilize themselves with slender, shallow roots. The flowers have 4 petals that are borne in loose clusters at the top of the stems. These flowers produce long, thin seed pods that hold up to 20,000 tiny black seeds per plant. These weeds can be found in ditches, forests, aquatic, and residential areas. The best control methods are repeated hand pulling before seed set. 

Downy Brome

NOXIOUS Downy Brome (Bromus tectorum) is an invasive grass species that is also a fire hazard. It is commonly overlooked as grasses don’t tend to be high on the list for invasive weeds. Downy Brome, also known as cheatgrass, can rapidly spread up to 5,000 seeds per plant. Downy Brome can be easily treated by hand-pulling, grazing or herbicides. Downy brome is a winter annual, native to the Mediterranean and belongs to the Poaceae family, also known as the grass family.

Downy Brome is reddish-purple at maturity and the flowering spike droops to one side. The awns are 7-20 cm long, twisted and covered with soft hairs that can irritate the mouths of livestock and wildlife. Leaf blades are long and covered with soft hairs and when pulled back, there is a white, papery thin ligule 1-3mm long, helping you distinguish it from other grasses. This plant has fibrous roots, and the plant's height depends on availability of moisture. This plant is regionally common and can be found in disturbed areas, crops, pastures, and Alberta’s most endangered ecosystem, grasslands. For any additional information on how to treat Downy Brome, please contact the Agriculture and Environmental department. 

Field Bindweed

Field Bindweed (Convolvulus arvensis) is also known as devil’s vine or wild morning glory. It is a perennial that is native to Africa, Asia and Europe. When it comes to reproduction, it can spread by seeds and creeping roots. The flowers are funnel shaped, white to pinkish in colour and about 2.5 cm in diameter. The flowers bloom in the summer and close when it is dark, raining or overcast. The leaves are dark green, arrowhead shaped and are alternately arranged on the vine-like stem. These plants have a deep taproot with extensive creeping roots that are whitish in colour, fleshy and brittle. This plant produces 500 seeds per plant and is viable for up to 60 years!  Field Bindweed prefers disturbed areas, pastures, cultivated fields and roadsides and are highly adaptive. Frequent hand pulling, cultivation or herbicides is best before seed set. This plant is problematic because it will host viruses that affect crops like tomatoes and potatoes and is mildly toxic to livestock. 

Garlic Mustard

PROHIBITED NOXIOUS Garlic Mustard (Alliaria petiolata) is an extremely invasive biennial plant that has recently been found in the Crowsnest Pass and northern Alberta. It is critical that all possible sightings of this plant are reported to the Agriculture and Environmental Department. This plant can invade undisturbed forests, aquatic areas, and residential areas. 

You can identify this plant by its heart-to-spade shaped leaves that have toothed edges. The toothed edges will gradually get smaller as the leaves move up the erect stems. From April to July, these weeds have small 4-petaled flowers that are white with yellow centers, measuring 1-1.5 cm across. The flowers form clusters at the end of the stems. A basal rosette is produced in the first stages of growth with a flowering stem in the second. Stems typically have 1-2 branches per plant and they stand tall up to 1.5 m. This plant has a slender taproot with an s-bend, or crooked root just below soil level. The fruit pods are up to 6 cm long and contain 850 seeds per plant.  

Garlic mustard prefers rich, moist, forest soils and can tolerate full sun or dense shade. This plant reproduces by seed, so hand-pulling is best as there are currently no registered herbicides for this plant. Other names for this biennial plant include Poorman’s mustard, Garlicwort and Jack-by-the-Hedge garlic. 

Hound's Tongue

NOXIOUS Hound’s Tongue (Cynoglossum officinale) is found in pastures, roadsides, and waste areas. It was introduced from Europe and belongs to the Borage family. It has toxic properties that can cause animals to have liver failure. Hound’s tongue is a biennial plant that has small reddish-purple flowers that are funnel-shaped hanging in small clusters from leaf axils from June to August. Being a biennial plant, it produces a basal rosette in the first year and then flowers in the second year. The leaves are oblong, up to 30 cm long and are hairy on both surfaces. The seed pods are known as ‘hitchhiker’ seeds with their prickly, bur-like pods. This plant grows up to 1.5 m in height, has branches to the top and is covered with hairs. This plant is regionally common, and found in forests, pastures, and disturbed areas. The best control measures are mechanical and chemical. 

Leafy Spurge

NOXIOUS Leafy Spurge (Euphorbia virgata) is an aggressive weed toxic to livestock, humans, and wildlife when consumed or when the milky sap touches the skin. The milky sap has been known to cause blindness and skin rashes so please handle with care. These plants can reproduce with creeping roots and seeds. Young leafy spurge, before flowering stage, can resemble noxious weed Yellow Toadflax, though Yellow Toadflax does not contain a milky sap. Leafy spurge is native to Asia and Europe and has unique disk shaped, yellow-green flowers from June to September. Leafy spurge is found in pastures, grasslands, and aquatic areas. The stems can grow up to 90 cm tall and develop deep, extensive creeping lateral roots. Small seeds grow in pods that explode and scatter up to 130,000 seeds in a 15 m radius. Sheep and goats can handle this noxious weed and have been used as a targeted control measure. Other control methods include herbicide or biocontrol using leafy spurge beetles.

Orange Hawkweed

PROHIBITED NOXIOUS Orange Hawkweed (Pilosella aurantiaca) is often referred to as Devil’s paintbrush but shares little resemblance with native species Red Paintbrush. Orange hawkweed is a perennial plant belonging to the Sunflower family. On the end of each stem, it has red-orange dandelion-like flowers and long hairs on the leaves and stem that can be seen from June to August, and sometimes through to September. The flowers are arranged in clusters and the bracts have coarse black hairs. Leaf edges could be smooth or slightly toothed. The erect stems grow up to 60 cm tall with few leaves. This weed can reproduce with fibrous, rhizomatic roots and mat-forming stolons. This weed produces up to 1,500 seeds per plant and, similar to dandelion seeds, they can easily travel by air. Hand pulling prior to flowering is a great control option but is important to note that treatment of flowering plants can facilitate seed production. This prohibited noxious plant has similar features to native hawkweeds although native hawkweeds tend to have leafy stems and do not have orange flowerheads.  

Oxeye Daisy

Oxeye Daisy (Leucanthemum vulgare) is a perennial that belongs to the Sunflower family and is native to Europe. You can spot these daisies by their yellow centered flowers that have 20-30 white petals located at the branch ends. The lower leaves are spoon-shaped and arranged alternately on the stems. The lower leaves are also lobed or have toothed edges and long leaf stalks whereas the upper leaves are narrow and clasped to the stem. The roots are short and fibrous making hand pulling an easy control method, but you want to make sure you dig the entire plant, removing the creeping, fibrous roots, and rhizomes to avoid regeneration. These plants tolerate a wide range of conditions and can be found almost anywhere. Buyer beware! This plant is often mixed into wildflower seed mixes! 

Scentless Chamomile

NOXIOUS Scentless Chamomile (Tripleurospermum inodorum) was introduced from Europe and can be found just about anywhere but commonly seen roadside, waste areas and cultivated fields during the months of June to September. The stems grow 20-100 cm tall, are hairless and odourless when crushed, living up to its name. The leaves have alternate arrangement, but it is the carrot-like leaves that differentiate it from Oxeye Daisy. Reports say that Scentless chamomile can produce over 300,000 seeds and remain dormant for several years. The stems are highly branched and can range from 5 cm to 100 cm tall. Scentless chamomile is a biennial or short-lived perennial that produces a basal rosette in its first year before turning into a reddish stemmed plant in its second year. This plant can handle a variety of conditions ranging from heavy clay soils, dry sites and flooded areas. You can control this plant by hand-pulling, herbicides, cultivation of rosettes though they may re-generate and bio-control agents. There is a seed-head feeding weevil and a gall midge which have been used to help control this noxious species. 

Spotted Knapweed

PROHIBITED NOXIOUS Spotted Knapweed (Centaurea stoebe) is perennial plant native to Eurasia belonging to the Sunflower family. These weeds have seed heads that persist until the following year and have distinct bracts that can be identified year-round with their dark, triangular fringed tips. 

Spotted knapweed has a grayish-green stem and leaves, and flowers from July to September. The flowers are pinkish-purple and develop on the end of the stem branch. This invasive plant is regulated as prohibited noxious because it exudes a chemical called catechin which prevents neighbouring plants from being able to germinate. It also has a deep taproot that helps compete for food and water. This short-lived perennial can reproduce by seeds and root fragments that resprout, enabling it to outcompete native vegetation. Spotted knapweed prefers well drained, light textured soils in full sun. They can be found in disturbed areas, fields, roadsides, and other open areas.  

When treating Spotted Knapweed, it is best to wear gloves and dig the entire plant out to avoid resprouting from taking place. These plants can also be treated with herbicides. Rosettes can be difficult to identify; if you need assistance, please don't hesitate to contact the Agriculture and Environmental Department for more information. 

Sulphur Cinquefoil

PROHIBITED NOXIOUS Sulphur Cinquefoil (Potentilla recta) is a long-lived perennial that has been recently found in the Crowsnest Pass. It has a very similar native cinquefoil species but can be distinguished by noticeable hairs on stem and leaves. Invasive Sulphur cinquefoil has pale yellow flowers with 5 deeply notched, rounded petals from June to July. It has 5 hairy sepals, palmately compound leaves with 5-7 toothed leaflets, it is important to note the underside of the leaf is green. Native cinquefoil species will have silver or different coloured underside. Sulphur cinquefoil has few basal leaves and many that grow along the stem. It will be 30-60 cm tall, and the stems will have perpendicular hairs. It has fibrous, woody roots and spreads up to 1400 seeds per season. This plant belongs to the rose family and the species name recta, means ‘erect’ or ‘upright’. 

If you believe you may have located this prohibited noxious plant, please report it to the Agriculture and Environmental Department or EDDMapS app.  

Tall Buttercup

NOXIOUS Tall Buttercup (Ranunculus acris) is native to Europe and has an upright yellow flower that sits on a long-branched stalk with a waxy appearance. This weed flowers from June to September and contains an irritating oil making it toxic to grazing animals, especially cattle. Tall buttercup can be controlled through cultivation, as the toxins dry up once the plant has been severed. If cultivation is the control method of choice, it is important to mow before seed set, and reseed with annual crop to avoid these plants reproducing by creeping roots. Tall buttercup prefers moist to well drained humus soils, however if sufficient moisture is available, they can handle coarse soils as well. You will find them in pastures, ditches, aquatic areas, and forests. Tall buttercup has 5 yellow petals, 5 small green sepals and has leaves that are deeply divided into 3-5 segments. Knowing how to identify to the leaves of Tall buttercup can help you differentiate them from native species Yellow Avens (Geum aleppicum) and non-native, prohibited noxious Sulphur Cinquefoil (Potentilla recta). Other control methods include herbicide and hand-pulling. 

Wild Caraway

NOXIOUS Wild Caraway (Carum carvi) also known as Common Caraway has been elevated to a noxious weed in the Crowsnest Pass. It is the property owner or occupiers’ responsibility to control this noxious plant and prevent further spread of its seeds. Wild Caraway is a biennial plant, meaning it grows a low-lying rosette the first year and then shoots up to a flowering plant in its second year. The rosette can be confused with native yarrow or wild carrot because it has finely divided leaves that appear fern-like. In its second year, the stems are usually glossy, grow up to 90 cm tall and are branched in the upper portion of the plant. The flowers form in umbel shaped clusters growing on long stalks. This weed flowers from May - August and the flowers have 5 heart-shaped petals that appear pale pink to white in colour. 


This plant is native to Eurasia and was brought to Canada for cultivation. It has since escaped and become established as an invasive species in some parts of Alberta. You can keep this plant under control by repeated hand-pulling and cutting down the plant before seed set. The seeds are evenly ribbed, 3 mm long, and break into 2 single-seeded segments. This plant is very delicate once seeds have been produced so if seeds are present, the best practice is to place a bag over top of the plant and close tightly around the stem to avoid dropping any seeds. If you believe you have some rosettes growing in your yard or if you have seen any of these invasive plants in the Crowsnest Pass, please contact the Agriculture and Environmental Department through our reporting website Omnigo Software - Online Reporting Main 

Yellow Toadflax

Yellow Toadflax (Linaria vulgaris) is a perennial, belongs to the Snapdragon family, native to Europe and is also known as butter-and-eggs! You can identify this plant by its yellow flowers that are attached by short stalks and the lower lip has an orange, fuzzy spot. The flowers are arranged in a dense cluster, or terminal raceme. The leaves are very narrow, alternate arrangement, pointed at each end and attached directly to the stem without clasping. These plants can tolerate a wide range of growing conditions and have an extensive creeping root system. They can also reproduce up to 5,000 seeds per plant! Repeated hand pulling is an easy control method for these woody, rhizomatous roots that may grow several meters long, herbicides work as well. Before this plant has flowered it is often confused with leafy spurge, however, this plant lacks the milky latex when broken apart!